Air core transformer



g 27 E. E. HOLMAN AIR CORE TRANSFORMER Filed May 27. 1925 Patented Aug. 16, 1927.

uulrsa STATES 1,638,996 rAT-ENT OFFICE.

EDWARD E. I-IOLMAN, or PORTLAND, OREGON.

; am 001m TRANSFORMER. 7

Application filed. May 27, 1925. Serial No. 33,129.

This invention relates generally to radio apparatus, and particularly to the construction of transformers for high frequencies.

The first object of this invention is to construct a special form of transformer for high frequencies in which the mutual inductance is relatively large, and in which the leakage and losses are reduced materially when compared wi 11 closed and open core transfornv ers such as are now in common use.

The second object is to so construct the transformer that it will be independent of any core or supporting frame.

The third object is to so construct the transformer that it will readily lend itself to manufacture, will be light in weight and occupy only a small amount of space.

The fourth object is to stabilize the receiving sets with which this transformer is used and to make same less susceptible to changes in capacity of nearby objects.

The fifth object is to so construct the transformer that the individual turns or coils of wire serve to support the adjacent coils at asuflicient number of points to make the completed transformer uniform in shape and extremely rigid in construction.

These results are accomplished in the manner set forth in the following specification as illustrated in the accompanying drawing, in which:

Figure 1 is an end elevation of the transformer showing only the first or odd number wraps or coils. l igure 2 is a similar view of the transformer showing only the second or even number of wraps or coils. Figure 3 is an end elevation of the transformer showing both sets of coils, but showing one set shaded in order that the paths of the different sets may be more easily followed. transformer showing the manner in-which the individual coils support each other, and also the manner in which the transformer is built up. 7

Similar numbers of reference refer to the same parts throughout the several views.

Referring in detail to the drawing, in order to illustrate the device and its peculiar construction I have indicated in Figures 1 and 2, in dotted lines, a base 10 having projecting therefrom the concentric pegs 11 to 17 inclusive and 18 to 2 1. It is on the pegs 11 to 2% that the transformer is wound, if constructed by hand. It must be understood,

Figure 4: is a side elevation of the.

however, that'after thetransformer linished it is removed from the. pegs and is without a material core of any kind. In other words, it is, truly speaking, an air core transformer since not even the usual cardboard or insulation core employed to hold same in position, it being preferable to mount same on one or two insulation pegs, or even suspending same entirely from the input or output lead wires.

For thesake of rendering the description more clear, no reference will be made to the secondary circuit except to state that it is wound in the same manner as is the primary. The number of turns in the secondary and the lateral placement thereof depends entirely upon factors not related to the present invention.

In order to wind this transformer a wire 25 of suitable diameter and covering is started from the outside of the concentric circle of pegs and threaded as follows: inside of peg 13, outside of 12, outside of 18, inside of 19, outside of 20, inside of 21, outside of 22, inside of 23, outside of 24, outside of 17, inside of 16, outside of 15, inside of 14: and outside of 13, thereby completing the first or odd number coils.

At the point 26 the wire 25 n'owstarts out on a new course as follows: inside of 12, outside of 11, outside of 19, inside of 20, outside of 21, inside of 22, outside of 23, outside of 16, inside of 15, outside of 1 1, inside of 18 to the point of beginning.

Throughout the illustration the wire 25 in the first coil27 is shown not shaded and the wire in the second coil 28 is shown shaded, in order to better illustrate their respective paths. V

Thetwo coils 27 and 28, it will be observed, assume somewhat the shape of a fig ure 8 whose upper and lower sides are so interwoven around the pegs and eventually secured by means of the binding cord 29 that' the finished product is one possessing a great degree of rigidity, and one whose number of turns or coils is not limited by undesirable piling at the intersections of the wires, since with this construction the piling is uniform throughout between the adjacent coils, causing the successive coils to build up on each other with complete uniformity.

In operation the external fields of these transformers is reduced to an exceedingly low value, presumably due to the manner in can be employed by interlacing the wires in difierent manners. For instance, if instead of winding same in andoutbetween ad acent pegs they could be wound outside of one and inside Oft-WVO and outside of the fourth and inside of the next two pegs. In this particular form I have illustrated the use of a fourteen peg winding form, which also is not essential, as can readily be understood.

1- am aware that air core transformers have been constructed in the past; I therefore do not claim such devices broadly, but I do intend to cover all such forms and modifications of the transformer above described as fall fairly Within the appended claim.

I claim:

An air core transformer consisting of a plurality of. superimposed interwoven coils each of which is substantially in the form of a figure Sovhose Outer portions are in alternate wave form and Whose inner portions are straight, said coils having the halves thereof wound in opposite directions, the

alternate coils having one of their inner portions out of alignment with a corresponding portion in the next adjacent coil but parallel thereto, and the second inner portion of each coil intersecting the corresponding portion of the next coil at a small angle; and means for holding said coils in rigid relation to each other.

EDWARD E. HOLMAN. 

